The present invention is directed to a column system for separation of particles, especially for magnetic separation of cells.
Magnetic cell separation is an established technology to separate magnetically labelled cells from non-magnetic cells by utilizing a high gradient magnetic field in which the magnetically labelled target cells are retained. Usually, a suspension of magnetically labelled cells and non-magnetic cells are guided through a column provided with a ferromagnetic matrix, which is subjected to a strong magnetic field. The magnetically labelled cells are retained on the ferromagnetic matrix, whereas the non-magnetic cells are eluted. The magnetically labelled cells may then be harvested by removing the column from the magnetic field and rinsing the cells from the matrix. This technology is for example described in U.S. Pat. Nos. 5,693,539 or 5,385,707.
The separation process is usually performed without applying pressure i.e. under normal gravity conditions, but enhanced pressure may be applied to speed up the process or to reduce the volume of the liquid. In this respect, U.S. Pat. No. 6,602,422 discloses a micro column system for magnetic cell separation provided with a plunger, which can be used to apply pressure in order to flush out liquid from the column.
In theory, such columns for magnetic cell separation can be used for several subsequent separation processes. However, most columns for magnetic cell separation are provided with a ferromagnetic matrix like a ferromagnetic mesh, steel wool, wire wool, wire sponge or ferromagnetic particles. If the liquid is removed from the matrix, for example by draining, air becomes entrapped in the ferromagnetic matrix. Due to the porous nature of the matrix, entrapped air can hardly be removed and blocks the matrix at least in part for further liquid. This results in a reduced separation speed, in worst case in a total stop of the separation process.
The plunger as disclosed in U.S. Pat. No. 6,602,422 might be used to force liquid (and entrapped air) through and out of the matrix, but by removing the plunger to add additional liquid, air is again sucked into the matrix, this time from the exit port of the column. In other words, the column described in U.S. Pat. No. 6,602,422 is not suitable for reuse, even with using the plunger.